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Hypothalamus and Pituitary Gland

Hypothalamus and Pituitary Gland

Author: Amanda Soderlind
Description:

Identify the hypothalamus and pituitary glands and the role they play in homeostasis.

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Tutorial

Hypothalamus and Pituitary Glands

Source: Video and Images Created by Amanda Soderlind

Video Transcription

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Welcome to this lesson today on the Hypothalamus and Pituitary Gland. Today, we are going to be discussing the role of the hypothalamus and pituitary gland in the endocrine system. So the hypothalamus and pituitary gland interact in order to control activities of various body organs and to help regulate homeostasis of the body.

So the hypothalamus and pituitary gland produce various different types of hormones that regulate these body organs and help maintain homeostasis of the body. And the hypothalamus and pituitary gland can be found in the brain. So if we take a look at our diagram right here, up in this region here would be the hypothalamus. And then down here, we would have the pituitary gland.

And the pituitary gland is actually made up of two separate lobes, each of which produces different hormones. So the anterior lobe of the pituitary gland makes and releases hormones. And then the posterior lobe stores and releases hormones from the hypothalamus. So here we have the anterior lobe, and here we have the posterior lobe.

So we have the hypothalamus again here, which is then working closely with the pituitary gland, which is composed of the anterior and posterior lobes. So we're going to start by taking a look at what happens in the posterior lobe of the pituitary gland. So basically within the hypothalamus up here, we have neurons. So you can see all of our neurons right here in green, and these neurons synthesize antidiuretic hormone and oxytocin.

So then basically what happens is these neurons have synthesized these two hormones, and these hormones will move down the axons of the neurons and they'll build up in our axon endings down here, which are located in the posterior lobe. So they're being produced up here in the hypothalamus, moving down the axons, and being stored in the axon endings located in the posterior lobe. So then when an action potential triggers a hormone release, the hormones will enter capillaries and then they'll be able to travel through the bloodstream to whatever their target cell is.

So as I mentioned, oxytocin is one of the hormones that's produced in the hypothalamus and then is stored in these axon endings of the neurons in the posterior lobe. So oxytocin plays a couple of different roles. One of its target cells is mammary glands. And in these mammary glands, it causes milk to move into the ducts.

And then it also acts on muscles in the uterus wall that cause contractions during childbirth. So oxytocin is this hormone basically that's active in women who are about to give birth or who have given birth. So It acts on those mammary glands in order to move milk into ducts, or to help with contractions during childbirth.

So oxytocin is one of them, and then antidiuretic hormone, also abbreviated ADH, is another hormone that's again produced in the hypothalamus and then is stored in the axon endings in this posterior lobe. An antidiuretic hormone plays a role in kidney nephrons, and basically what it does is it causes water to be conserved in those kidney nephrons. So oxytocin and ADH are stored in the posterior lobe of the pituitary gland.

If we take a look at our anterior lobe, the way that this works is a little bit different. So we have these neurons up here in the hypothalamus that will secrete certain hormones. And then, those hormones will be picked up by capillaries at the base of the hypothalamus. So we have the hormones secreted here, moving down the axons. And then at the base of the hypothalamus, those hormones will be picked up by capillaries and they'll be delivered to a capillary bed in the anterior lobe here.

So then molecules of those hormones will act on endocrine cells in the anterior lobe. And then, hormones from the anterior lobe cells will enter blood vessels and then will be carried through the bloodstream in that manner. So these here are the hormones that are released by the anterior lobe of the pituitary gland.

So we're going to start by talking about growth hormone, which is sometimes abbreviated GH. So growth hormone is a hormone that regulates a person's growth. That is secreted by this anterior lobe.

Prolactin, abbreviated PRL, basically prolactin plays a role in milk production in mammary glands. Luteinizing hormone, LH, plays a role in the reproductive system. It also helps with the secretion of other hormones and it's found mostly in the ovaries and testes, so it's a part of the reproductive system.

Follicle stimulating hormone, FSH, is another hormone that plays a role in the reproductive system, so it's found in ovaries and testes, and it plays a role in gamete formation. Thyroid stimulating hormone, or TSH, is a hormone that controls the release of thyroid hormone. And then our last one here is adrenocorticotropic, which is abbreviated ACTH, and this hormone stimulates the release of cortisol from the adrenal glands. So these are all the various different hormones that are secreted by the anterior lobe. So this lesson has been an overview on the role of the hypothalamus and pituitary gland in the endocrine system.

Growth Hormone Disorders

Source: Video and Images Created by Amanda Soderlind

Video Transcription

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Welcome to this lesson on growth hormone. Today we will be discussing the role of the growth hormone in the body and also the role that it plays in the endocrine system. So the growth hormone is a hormone that secreted by the anterior lobe of the pituitary gland, and the pituitary gland is located in the brain. So sometimes the regulation of this hormone can get a little off whack. So sometimes too much of this hormone can be secreted, and sometimes too little of this hormone can be secreted. And so if too much or too little is secreted, it can lead to some sort of abnormal growth.

So right here where I have GH, this stands for growth hormone. That's an abbreviation for growth hormone. So if too much growth hormone is secreted by the anterior leg of the pituitary gland, it can lead to a disorder called gigantism. So gigantism is-- a condition in which too much hormone is released during childhood. And basically the outcome is a person that is much larger than average. So the person will have normal body proportions. However, they will be much taller and much larger than the average person because this anterior lobe of the pituitary gland is secreting too much growth hormone.

So normally growth hormone regulates how tall we get and the epiphyseal plates of our bones in conjunction with growth hormone, help a person reach a normal height. But if too much growth hormone is being secreted, then the person is going to be much taller than they normally would. The bones are allowed to continue to grow abnormally.

Growth hormone overproduction can also affect adults. So in this disorder it's affecting children. So children are growing too tall, but if something happens where once a person reaches adulthood and growth hormone starts being overproduced, the person is not going to be able to grow any taller because epiphyseal plates have calcified over. So instead what happens is that tissues become thicker. So basically tissues like the bone, skin, cartilage, the tissues of like the face, the hands, the feet are all going to become abnormally thick. So the person is not going grow any taller, but their tissues will become thicker. So this is another way that growth hormone overproduction can effect a person.

On the other hand, sometimes too little growth hormone can be secreted. So if not enough or too little growth hormone is secreted, it can lead to pituitary dwarfism. And in pituitary dwarfism, basically the anterior lobe under produces growth hormone, or it's not producing enough growth hormone. So the result will be a person that is really short, but with normal proportions again. So body proportions are normal, but the person is to just going to be shorter than average. And pituitary dwarfism can actually be inherited or if there is some sort of injury or tumor that affects the pituitary, it can also affect the amount of growth hormone being released.

So sometimes if this is detected in children while they're still growing, they can receive shots of artificial growth hormone, which will then increase the growth hormone levels and help them grow to an average height. However, it's very expensive, and it's also a big ethical debate. People don't think that artificial growth hormone should be used to treat these disorders. So growth hormone disorders can be a result of too much or too little growth hormone being secreted into the body. So this lesson has been an overview on disorders associated with the growth hormone.

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Terms to Know
Acromegaly

A condition in which growth hormone levels are too high after growth plates ossify; this causes bones to thicken and extremities to enlarge but bones cannot grow in length. The most prominent signs are enlarged facial features, hands and feet.

Anterior Lobe of Pituitary Gland

Also called the adenohypophysis, the anterior lobe of the pituitary gland started developing in the nasopharynx and migrated up into the skull to join with the posterior lobe of the pituitary gland. Since the anterior pituitary didn’t originate in the brain there are no direct neural connections to it. The anterior pituitary gland secretes six hormones: growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH), prolactin, luteinizing hormone (LH), and follicle stimulating hormone (FSH).

Gigantism

A condition in which growth hormone levels are too high at an age before growth plates ossify; this causes bones and other tissues to grow proportionally larger than average.

Hypothalamus

A part of the forebrain that works closely with the pituitary gland to monitor the body's organs and their functioning.

Pituitary Dwarfism

A condition in which growth hormone levels are too low at a young age and the person is proportionally smaller than normal.

Pituitary Gland

Called the “master gland” because of its effects on other glands; endocrine hormones increase activity/secretion of many major glands of the endocrine system.

Posterior Lobe of Pituitary Gland

Also called the neurohypophysis, the posterior lobe of the pituitary gland developed from brain tissue during embryonic development and therefore is directly innervated by the hypothalamus. The two hormones the posterior pituitary secretes are anitdiuretic hormone (ADH) and oxytocin.